Bibliographic details of references provided in the subject specification are listed at the end of the specification.
Reference to any prior art is not, and should not be taken as, an acknowledgment of or any form of suggestion that this prior art forms part of the common general knowledge in any country.
Th2 cytokines, IL-4, IL-5, IL-9 and IL-13, are derived from T helper type 2 (Th2) cells, although they may also derive from other cell types. These Th2 cytokines play an important role in the pathophysiology of allergic diseases including asthma.
Asthma is a chronic disease that involves inflammation of the pulmonary airways and bronchial hyper-responsiveness leading to reversible obstruction of the lower airways (reviewed in Bousquet et al, Am J Respir Crit Care Med 161(5):1720-1745, 2000). In a diagnostic context bronchial hyper-responsiveness is evidenced by decreased bronchial airflow following exposure to methacholine or histamine. Natural triggers that provoke airway obstruction include respiratory allergens, cold air, exercise, viral upper respiratory infection, and cigarette smoke. Bronchial provocation with allergen induces a prompt early phase immunoglobulin E (IgE)-mediated decrease in bronchial airflow followed in many patients by a late-phase IgE-mediated reaction with a decrease in bronchial airflow for 4-8 hours.
Asthmatic airways display lung hyperinflation, smooth muscle hypertrophy, fibrosis in the lamina reticularis, mucosal edema, epithelial cell sloughing, cilia cell disruption, and mucus gland hypersecretion. Microscopically, asthma is characterized by the presence of increased numbers of eosinophils, mast cells, neutrophils, lymphocytes, and plasma cells in the bronchial tissues, bronchial secretions, and mucus. Activated CD4 T-lymphocytes that produce a Th2 pattern of cytokines appear to be central to the initiation, development and maintenance of the disease phenotype (Robinson et al, N Engl J Med 326(5):298-304, 1992; Wills-Karp et al, Science 282(5397):2258-2261, 1998; Hamid et al J Clin Invest 87(5):1541-1546, 1991; Ray and Cohn, J Clin Invest 104(8):985-993, 1999). For example, the cytokines produced by these cells (including IL-4, IL-5, IL-9 and IL-13) regulate infiltration and mediator release by inflammatory cells and allergen specific antibody isotype switching from IgM to IgE. The activity of non-hemopoietic cells, for example mucus hypersecretion by goblet cells, is also regulated by Th2 cytokines.
Regardless of the triggers of asthma, the repeated cycles of inflammation in the lungs with injury to the pulmonary tissues followed by repair may produce long-term structural changes (“remodeling”) of the airways.
In the most widely used animal model of human asthma, mice are sensitized to ovalbumin (ova, formulated in alum adjuvant) via the intraperitoneal route on one or more occasions. An allergic airway response is subsequently induced by single or repeated exposure to aerosol ova (generated via and ultrasonic nebulizer). Response parameters assessed over the subsequent 24-72 hr period include, for example, the accumulation of inflammatory cells and mediators in bronchoalveolar lavage (BAL) fluid, bronchorestriction following intravenous administration of methacholine (airway hyper-reactivity) and ova specific serum IgE. Histological demonstration of inflammatory cell accumulation in lung tissues and goblet cell hyperplasia/metaplasia and associated mucus hypersecretion are also key characteristics of the mouse airway response to ova. Large animal models of asthma (for example non-human primates and sheep), where lung architecture, circulation and innervation more closely resemble that of humans, have been described but are less widely used. At the time studies described in this specification were performed there were no reports of the analysis of IL-11 antagonists in either small or large animal models of asthma.
IL-11 is a pleiotropic cytokine produced by a wide variety of cell types including fibroblasts, epithelial cells, chondrocytes, endothelial cells, osteoblasts and certain tumor cells and cell lines (reviewed in Neben and Turner, Stem Cells. Suppl 2:156-62 1993, Du and Williams, Blood. 83(8):2023-2030, 1994). Human IL-11 is synthesized as a 19 kDa 199 amino acid precursor protein, with a 21 amino acid leader sequence that is removed to generate a mature secreted protein of 178 amino acids. IL-11 is highly conserved across species—the mature human and murine proteins share 88% homology at the amino acid level, while human and non-human primate IL-11 share 94% homology. Although the crystal structure of IL-11 has not been solved a variety of approaches (e.g. computer modeling and alanine scanning mutagenesis) suggest a 4 α-helical bundle structure typical of many cytokines (Czupryn et al, Ann N Y Acad Sci 762:152-164, 1995).
IL-11 was originally described as a soluble factor derived from stromal cells, which was capable of stimulating plasmacytoma cell proliferation (Paul et al, Proc. Nat. Acad Sci. 87:7512-7516, 1990). A variety of diverse biological properties have subsequently been ascribed to IL-11 including: the ability to stimulate hemopoiesis, thrombopoiesis, megakaryopoiesis (Nandurkar et al, Blood 90:2148, 1997; Nakashima et al, Semin Hematol 35(3):210-221, 1998), and bone resorption (Sims et al, J Bone Miner Res 20(7):1093-1102, 2005); the regulation of macrophage differentiation (Romas et al, J Exp Med 183(6):2581-2591, 1996); the regulation of proinflammatory cytokine synthesis including TNFα and IL-1β (Leng et al, J Immunol 159(5):2161-2168, 1997; Hermann et al, Arthritis Rheum 41(8):1388-1397, 1998; Trepicchio et al, J Immunol 159(11):5661-5670, 1997); the ability to confer mucosal protection after chemotherapy and radiation therapy (Orazi et al, Lab Invest 75(1):33-42, 1996); and as an absolute requirement for normal development of placentation and survival to birth (Robb et al, Nat Med 4:303, 1998). A number of these biological properties have been exploited in the development of new therapeutic strategies. Recombinant human IL-11 has been approved as a treatment for chemotherapy induced thrombocytopenia (Tepler et al, Blood 87(9):3607-3614, 1996) and is currently being assessed as a new approach to the treatment of chemotherapy induced gastrointestinal mucositis (Herrlinger et al, Am J Gastroenterol 101(4):793-797, 2006). Treatment with recombinant IL-11 in a mouse model of rheumatoid arthritis (collagen induced arthritis, CIA) caused a significant reduction in the severity of established disease, which was associated with protection from joint damage, as assessed by histology (Walmsley et al, Immunology 95(1):31-37, 1998). In a subsequent Phase I/II clinical study patients receiving a once weekly dose of IL-11 (15 μg/kg) demonstrated a significant reduction in the number of tender joints, although there was no overall benefit at the ACR criterion of a 20% response (Moreland et al, Arthritis Res 3(4):247-252, 2001). Similarly, IL-11 has shown therapeutic benefit in animal models of inflammatory bowel disease (IBD; Peterson et al, Lab Invest 78(12):1503-1512, 1998) and this prompted clinical studies to assess the safety and efficacy of IL-11 in patients with active Crohns disease. While IL-11 was well tolerated and provided some clinical benefit, it remained significantly inferior when compared with a standard steroid based therapy (Herrlinger et al, supra 2006).
In addition to arthritis and IBD, IL-11 has also been demonstrated to provide therapeutic benefit in mouse (Lai et al, Nephron Exp Nephrol 101(4):e146-154, 2005) and rat (Lai et al, J Am Soc Nephrol 12(11):2310-2320, 2001) models of glomerulonephritis. In these models, inflammatory disease is induced via the administration of ‘nephrotoxic serum’ (generated by immunization of donor animals, for example sheep, with mouse or rat glomeruli preparations) and is assessed through standard histological and urine analysis. IL-11 therapy resulted in a significant reduction in albuminuria at 24 hrs as well as a decrease in fibrinogen deposition and infiltrating inflammatory cells at 14 days post induction of disease (Lai et al, supra 2005).
In addition, IL-11 has been suggested as a potential therapeutic agent in various other inflammatory disorders including radiation-induced lung damage (Redlich et al, J Immunol 157(4):1iO5 10, 1996), sepsis (Chang et al, Blood Cells Mol Dis 22(1):57-67, 1996) and psoriasis (Trepicchio et al, J Clin Invest 104(11):1527-1537, 1999). U.S. Pat. No. 6,270,759 suggests that IL-11 may be therapeutically useful for a variety of inflammatory conditions including asthma and rhinitis.
The biological properties of IL-11 (IL-11 activity) are mediated through a multimeric receptor complex that incorporates IL-11, the IL-11Rα chain and gp130 (reviewed in Taga, J Neurochem 67(1): 1-10, 1996) and referred to as the IL-11 receptor complex. The IL-11Rα chain binds directly to IL-11 with low affinity (kDa ˜10 nM), is unique to the IL-11 receptor complex and is responsible for conferring specificity. gp130 is a shared receptor component used by members of the IL-6 ligand family (IL-6, IL-11, LIF, OSM and CNTF) and is responsible for the activation of intracellular signal transduction, primarily via the JAK/STAT pathway. Recent data suggests that the IL-11 receptor complex is a high affinity (kDa ˜400-800 pM), hexameric complex that incorporates two molecules of IL-11, two molecules of IL-11Rα and two molecules of gp130 (Barton et al, J Biol Chem 275(46):36197-36203, 2000).
In contrast to the potential therapeutic approaches using IL-11, antagonists of IL-11 or IL-11R have been suggested as potential therapeutics for the treatment of osteoporosis (WO9959608) and in view of the role of IL-11 in the development of placentation and survival to birth (Robb et al, supra 1998) as a contraceptive agents (WO9827996 and WO03099322).
The role of IL-11 as a mediator of airway inflammation (including asthma) has primarily been investigated in mouse models, where one approach has been to assess the impact of increasing local IL-11 concentrations, Strategies used to achieve such an increase have included the local administration of recombinant IL-11 protein or local de novo synthesis via a lung specific IL-11 transgene. The results of these studies have not been definitive and, in the context of airways disease such as asthma, the potential of IL-11 either as a target or as a novel therapeutic has remained unclear.
Einarsson et al, J Clin Invest 97(4):915-924, 1996 demonstrated that respiratory pathogens linked to asthma exacerbation (in contrast to other viral and bacterial pathogens) were potent stimulators of lung stromal cell IL-11 production in vitro. Consistent with this observation, IL-11 was readily detectable in aspirates from children with upper respiratory tract infections but not in aspirates from uninfected children—interestingly the highest levels of IL-11 were detected in aspirates from children with clinical bronchospasm. When instilled into the lungs of mice, recombinant IL-11 induced a marked increase in sensitivity to methacholine and a mild mononuclear inflammatory response. In a subsequent report Tang et al, J. Clin. Invest. 98:2845, 1996 generated transgenic mice in which constitutive over-expression of IL-11 was targeted to the lung using the CC-10 promoter (CC-10/IL-11 Tg mice). In contrast to wildtype (wt) littermate controls, the transgenic animals demonstrated a nodular peribronchiolar mononuclear infiltrate with significant airways remodeling and sub-epithelial fibrosis. Furthermore, by two months of age the transgenic mice demonstrated increased airways resistance and airways hyperresponsivness to methacholine when compared with their wt littermates.
While the above studies suggest that IL-11 overexpression may contribute to the development of experimental airways inflammation, a potential role for IL-11 in the pathology of asthma is less clear. For example, cell populations known to be central to the development of asthma pathology such as eosinophils and mast cells were not detected in the infiltrates induced by IL-11. Nevertheless IL-11 mRNA and protein has been detected in the epithelial and sub-epithelial layers of human bronchial biopsies, with levels significantly greater in moderate and severe asthmatics compared to patients with mild disease and non-asthmatics (Minshall et al, J Allergy Clin Immunol 105(2 Pt 1):232-238, 2000).
To address this particular issue more directly Wang et al, J. Immunol. 165:2222, 2000 assessed the development of experimental asthma (OVA sensitization model) in the CC-10/IL-11 Tg mice. As expected OVA challenge of sensitized wt mice caused airway eosinophilic inflammation, Th2 cell accumulation, and mucus hypersecretion with mucus metaplasia. Increased levels of endothelial cell VCAM-1, mucin (Muc) 5ac gene expression and bronchoalveolar lavage and lung IL-4, IL-5, and IL-13 protein and mRNA were also noted. In contrast, OVA challenged CC10/IL-11 Tg mice that overexpressed IL-11 in the lung demonstrated lower levels of tissue and bronchoalveolar lavage inflammation, eosinophilia, and Th2 cell accumulation, and significantly lower levels of VCAM-1 and IL-4, IL-5, and IL-13 mRNA and protein. These studies demonstrate that IL-11 selectively inhibits many of the hallmarks of asthma pathology and prompted the authors to suggest that recombinant IL-11 might be used as a treatment for Th2 mediated disorders such as asthma.
More recent studies in the development of Th2 mediated disease have only served to add an additional layer of complexity (Chen et al, J Immunol 174(4):2305-2313, 2005). The Th2 cytokine IL-13 has been demonstrated to be key to the development of several aspects of asthma pathology including eosinophillic inflammation, mucus hypersecretion, airways hyper-responsiveness and allergen specific IgE. In agreement with these data lung-specific transgenic overexpression of IL-13 (CC-10/IL-13 Tg mice) results in the development of a severe Th2/asthma-like phenotype (Zhu et al, J Clin Invest 103(6):779-788, 1999). To assess a putative role for IL-11 in IL-13 activity (Chen et al, supra 2005) compared the expression of IL-11, IL-11Rα, and gp130 in lungs from wild-type mice and CC-10/IL-13 Tg mice and characterized the effects of a null mutation of IL-11Rα on the development of lung pathology in CC-10/IL-13 Tg mice. IL-13 was demonstrated to be a potent stimulator of IL-11 and IL-11Rα. Furthermore many of the pathological consequences of IL-13 overexpression, including inflammation, fibrosis, and mucus metaplasia, were substantially ameliorated in the absence of IL-11Rα. This led to the conclusion that IL-11Rα plays a key role in the pathogenesis of IL-13-induced inflammation and remodeling.
Accordingly, with respect to airway-inflammation the role of IL-11 remains unclear. In contrast, for non-airway inflammatory disease, the use of recombinant IL-11 as a novel therapeutic agent is well supported by published data.
There is a need to develop new treatments for Th2-mediated disorders such as asthma.